1. Field of the Invention
The invention relates in general to a liquid crystal display device, and more particularly to the test architecture for a liquid crystal display.
2. Description of the Related Art
FIG. 1 is a schematic illustration showing a test architecture for a conventional liquid crystal display panel 100. Referring to FIG. 1, the liquid crystal display panel 100 has a plurality of data lines DL(1) to DL(N) and a plurality of pixel circuits P, wherein N is a positive integer. The liquid crystal display panel 100 has a plurality of test pads TP(1) to TP(N), which corresponds to the data lines DL(1) to DL(N) and is used to test the pixel circuits P, on a glass substrate 102. For example, the display panel 100 has 2048 test pads TP(1) to TP(2048) if it has 2048 data lines DL(1) to DL(2048). These test pads TP(1) to TP(2048) receive pixel voltages to test each pixel circuit P and thus determine whether each pixel circuit is normal in the process of manufacturing the liquid crystal display panel 100, such as in the phase when the glass substrate 102 has been manufactured but the liquid crystal is not filled and the opposite glass substrate is not assembled (the procedure in the array manufacturing process). That is, the pixel voltages are sequentially transferred to the corresponding pixel circuits P through the 2048 test pads TP(1) to TP(2048) and the 2048 data lines DL(1) to DL(2048). Then, the voltage levels stored in the pixel circuits P are measured through the 2048 test pads TP(1) to TP(2048), respectively, and whether the functions of the pixel circuits P are normal can be detected.
Although the above-mentioned method can definitely detect whether the function of each pixel circuit P is normal, the problems in the high cost and the manufacturing difficulty exist. In other words, these problems are that the number of the test pads TP corresponding to the data lines DL greatly increases when the resolution is higher. The greater number of test pads TP increases the manufacturing cost of the glass substrate 102, and there is no sufficient space for the test probes to be inserted into the test pads, or there is even no sufficient space for accommodating these test pads TP on the glass substrate 102 because the density of the test pads TP is higher.
According to the consideration of the cost and the manufacturing difficulty, the actual number of test pads of the conventional display panel does not correspond to the number of the data lines in a one-to-one manner. In the prior art, some data lines share one test pad, such that the number of test pads disposed on the liquid crystal display panel is reduced. For example, three or six data lines share one test pad. However, this architecture cannot precisely detect whether each pixel circuit works normally when the glass substrate is manufactured, that is, when the liquid crystal is not filled in and the opposite glass substrate is not assembled. This architecture can only know that at least one pixel circuit among the pixels connected to the data lines corresponding to some test pad has a fault.
Thus, it is an important subject of the panel industry to solve the problem by precisely detecting the functions of the pixel circuits when the glass substrate is manufactured, and to solve the problems of the difficult tests or arrangements due to the too-high density of the test pads.